/*

 * Copyright (c) 1996, 2011, Oracle and/or its affiliates. All rights reserved.

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.  Oracle designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Oracle in the LICENSE file that accompanied this code.

 *

 * This code is distributed in the hope that it will be useful, but WITHOUT

 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

 * or visit www.oracle.com if you need additional information or have any

 * questions.

 */

package java.io;

/**

 * A buffered character-input stream that keeps track of line numbers.  This

 * class defines methods {@link #setLineNumber(int)} and {@link

 * #getLineNumber()} for setting and getting the current line number

 * respectively.

 *

 * <p> By default, line numbering begins at 0. This number increments at every

 * <a href="#lt">line terminator</a> as the data is read, and can be changed

 * with a call to {@code setLineNumber(int)}.  Note however, that

 * {@code setLineNumber(int)} does not actually change the current position in

 * the stream; it only changes the value that will be returned by

 * {@code getLineNumber()}.

 *

 * <p> A line is considered to be <a id="lt">terminated</a> by any one of a

 * line feed ('\n'), a carriage return ('\r'), or a carriage return followed

 * immediately by a linefeed.

 *

 * @author      Mark Reinhold

 * @since       1.1

 */

public class LineNumberReader extends BufferedReader {

    /** The current line number */

    private int lineNumber = 0;

    /** The line number of the mark, if any */

    private int markedLineNumber; // Defaults to 0

    /** If the next character is a line feed, skip it */

    private boolean skipLF;

    /** The skipLF flag when the mark was set */

    private boolean markedSkipLF;

    /**

     * Create a new line-numbering reader, using the default input-buffer

     * size.

     *

     * @param  in

     *         A Reader object to provide the underlying stream

     */

    public LineNumberReader(Reader in) {

        super(in);

    }

    /**

     * Create a new line-numbering reader, reading characters into a buffer of

     * the given size.

     *

     * @param  in

     *         A Reader object to provide the underlying stream

     *

     * @param  sz

     *         An int specifying the size of the buffer

     */

    public LineNumberReader(Reader in, int sz) {

        super(in, sz);

    }

    /**

     * Set the current line number.

     *

     * @param  lineNumber

     *         An int specifying the line number

     *

     * @see #getLineNumber

     */

    public void setLineNumber(int lineNumber) {

        this.lineNumber = lineNumber;

    }

    /**

     * Get the current line number.

     *

     * @return  The current line number

     *

     * @see #setLineNumber

     */

    public int getLineNumber() {

        return lineNumber;

    }

    /**

     * Read a single character.  <a href="#lt">Line terminators</a> are

     * compressed into single newline ('\n') characters.  Whenever a line

     * terminator is read the current line number is incremented.

     *

     * @return  The character read, or -1 if the end of the stream has been

     *          reached

     *

     * @throws  IOException

     *          If an I/O error occurs

     */

    @SuppressWarnings("fallthrough")

    public int read() throws IOException {

        synchronized (lock) {

            int c = super.read();

            if (skipLF) {

                if (c == '\n')

                    c = super.read();

                skipLF = false;

            }

            switch (c) {

            case '\r':

                skipLF = true;

            case '\n':          /* Fall through */

                lineNumber++;

                return '\n';

            }

            return c;

        }

    }

    /**

     * Read characters into a portion of an array.  Whenever a <a

     * href="#lt">line terminator</a> is read the current line number is

     * incremented.

     *

     * @param  cbuf

     *         Destination buffer

     *

     * @param  off

     *         Offset at which to start storing characters

     *

     * @param  len

     *         Maximum number of characters to read

     *

     * @return  The number of bytes read, or -1 if the end of the stream has

     *          already been reached

     *

     * @throws  IOException

     *          If an I/O error occurs

     *

     * @throws  IndexOutOfBoundsException {@inheritDoc}

     */

    @SuppressWarnings("fallthrough")

    public int read(char cbuf[], int off, int len) throws IOException {

        synchronized (lock) {

            int n = super.read(cbuf, off, len);

            for (int i = off; i < off + n; i++) {

                int c = cbuf[i];

                if (skipLF) {

                    skipLF = false;

                    if (c == '\n')

                        continue;

                }

                switch (c) {

                case '\r':

                    skipLF = true;

                case '\n':      /* Fall through */

                    lineNumber++;

                    break;

                }

            }

            return n;

        }

    }

    /**

     * Read a line of text.  Whenever a <a href="#lt">line terminator</a> is

     * read the current line number is incremented.

     *

     * @return  A String containing the contents of the line, not including

     *          any <a href="#lt">line termination characters</a>, or

     *          {@code null} if the end of the stream has been reached

     *

     * @throws  IOException

     *          If an I/O error occurs

     */

    public String readLine() throws IOException {

        synchronized (lock) {

            String l = super.readLine(skipLF);

            skipLF = false;

            if (l != null)

                lineNumber++;

            return l;

        }

    }

    /** Maximum skip-buffer size */

    private static final int maxSkipBufferSize = 8192;

    /** Skip buffer, null until allocated */

    private char skipBuffer[] = null;

    /**

     * Skip characters.

     *

     * @param  n

     *         The number of characters to skip

     *

     * @return  The number of characters actually skipped

     *

     * @throws  IOException

     *          If an I/O error occurs

     *

     * @throws  IllegalArgumentException

     *          If {@code n} is negative

     */

    public long skip(long n) throws IOException {

        if (n < 0)

            throw new IllegalArgumentException("skip() value is negative");

        int nn = (int) Math.min(n, maxSkipBufferSize);

        synchronized (lock) {

            if ((skipBuffer == null) || (skipBuffer.length < nn))

                skipBuffer = new char[nn];

            long r = n;

            while (r > 0) {

                int nc = read(skipBuffer, 0, (int) Math.min(r, nn));

                if (nc == -1)

                    break;

                r -= nc;

            }

            return n - r;

        }

    }

    /**

     * Mark the present position in the stream.  Subsequent calls to reset()

     * will attempt to reposition the stream to this point, and will also reset

     * the line number appropriately.

     *

     * @param  readAheadLimit

     *         Limit on the number of characters that may be read while still

     *         preserving the mark.  After reading this many characters,

     *         attempting to reset the stream may fail.

     *

     * @throws  IOException

     *          If an I/O error occurs

     */

    public void mark(int readAheadLimit) throws IOException {

        synchronized (lock) {

            super.mark(readAheadLimit);

            markedLineNumber = lineNumber;

            markedSkipLF     = skipLF;

        }

    }

    /**

     * Reset the stream to the most recent mark.

     *

     * @throws  IOException

     *          If the stream has not been marked, or if the mark has been

     *          invalidated

     */

    public void reset() throws IOException {

        synchronized (lock) {

            super.reset();

            lineNumber = markedLineNumber;

            skipLF     = markedSkipLF;

        }

    }

}